Actually, this code will produce a PNG file, thus it will set the header to ‘Content-type: image/png‘. Once the header is set, it cannot be changed. Now let’s see what happens if you try to mix it with HTML:

However, if the data is complicated, it would be better to include JpGraph directly in your PHP. This way, JpGraph has access to the necessary data structures from which it can construct the graph. I will explain it in the next section.

As you can see, at the beginning of the page we show some HTML text that is followed by the graph. The data of the graph is produced by our PHP, and JpGraph’s PHP has direct access to it, thus no parameter passing is necessary.

The idea is the following: the graph is written to the file system. Then, this file is shown using the <img src="..."> tag. A time limit is set (here 3 minutes). When the script is called again, it’ll automatically remove images that are older than the limit.

Unfortunately, the image cannot be deleted right after the <img src="..."> tag. When your browser sees this tag, it’ll launch a thread to fetch the image and steps on. That is, the image would be deleted immediately after the creation, and the browser couldn’t show it. So the image file must be left there. My solution is to set a time limit, and when the PHP page is called again, it’ll remove the old images. This way you’ll always have some temporary images in the temp folder, but not many.

Preparation:

I suppose you have your PHP script in your ~/public_html directory. Here create a temporary directory for the images called tmp.jpgraph and set its permission to 777 (chmod 777 tmp.jpgraph).

“JpGraph is an Object-Oriented Graph creating library for PHP >= 5.1 The library is completely written in PHP and ready to be used in any PHP scripts (both CGI/APXS/CLI versions of PHP are supported).”

If you want to draw graphs in PHP, JpGraph is a good choice. Very easy to use yet powerful.

Installation

Here I suppose you have a public_html directory in your HOME and your PHP scripts are in public_html.

Download the latest jpgraph archive, put it in ~/public_html/lib and extract it. Now you will have a directory like ~/public_html/lib/jpgraph-3.5.0b1. Put a symbolic link on it with a simpler name:

cd ~/public_html/lib
ln -s jpgraph-3.5.0b1 jpgraph

Verify if the directory jpgraph has the correct permissions. Directories must be 755, while files must be 644. To correct permissions, you can use this script: